Lower extremity amputation causes rapid changes in musculoskeletal system. With the effect of these changes, the energy requirement for prosthetic ambulance is much higher than normal ambulance. Although methods such as the reduction of the segmental load of the prosthesis and the preference of the different prosthetic components for energy expenditure have been emphasized, the effect of exercise types has not been investigated in our knowledge. Therefore, the aim of the current study is to investigate the effect of spinal (Core) stabilization exercises on energy expenditure in combination with the classical physiotherapy program in patients with unilateral transtibial amputation. Individuals with transtibial amputation included in the study will be randomly divided into two groups. In group 1, basic exercises related to amputation will be applied for 8 weeks and in group 2 basic exercises with spinal stabilization exercises will be applied to the individuals. At the beginning and at the end of the exercise intervention, energy expenditure and exercise capacity will be evaluated by a portable exercise test device during '6 Minutes Step Test'; fatigue assessment will be done before and after 6 Minutes Step Test with 'Modified Borg Scale'; the strength of deep spinal muscles will be evaluated with 'Stabilizer'; dynamic balance and functional mobility will be evaluated by 'Timed Up & Go' Test; and the effect of the prosthesis on mobility will be evaluated by the sub-scale 'Mobility' of 'Prosthetic Evaluation Questionnaire'.

Inclusion Criteria:

• Having unilateral transtibial amputation of at least 6 months in which the stump volume becomes stable,
• Being prosthetic users (For homogenization of the groups in terms of external support used, individuals with transitibial amputation included in the study should use total contact socket and carbon foot prosthesis systems - Pin System, Passive Vacuum System or Active Vacuum System),
• Having at least "four" quadriceps and hamstring muscle strength in the amputated limb according to Lovett's manual muscle test method.

Exclusion Criteria:

• Having any disadvantage about prosthetic device usage in terms of stump length, shape and edema,
• Having movement limitation,
• Having phantom pain in the stump,
• Having any discomfort or health problem (cardiopulmonary, neurological or orthopedic problems) that may affect gait other than amputation,
• Having multiple extremity loss.